Jnario is a framework for writing executable specifications for Java. It provides all the goodness of Xtend while being specifically tailored to writing acceptance and unit tests. It is easy to integrate as Jnario specifications are compiled to plain Java Junit tests.

BDDfy is a simplest BDD framework for .NET. It can run with any testing framework. Actually you don't have to use a testing framework at all. You can just apply it on your POCO (test) classes! It does not need a separate test runner. You can use your runner of choice. For example, you can write your BDDfy tests using NUnit and run them using NUnit console or GUI runner, Resharper or TD.Net and regardless of the runner, you will get the same result.

NBehave is a framework for Behaviour-Driven Development Behaviour-driven development (BDD) is an evolution of test-driven development (TDD) and acceptance-test driven design, and is intended to make these practices more accessible and intuitive to newcomers and experts alike

PyVows is an asynchronous behaviour driven development (BDD) for Python. The main reason for asynchronous testing is to make tests which target I/O run much faster, by running them concurrently. By having a faster suite, it gets run that more often, thus improving the feedback cycle.

Watai (Web Application Testing Automation Infrastructure) is a declarative, bottom-up BDD, full-stack web testing framework. It is both a test runner engine (i.e. it executes tests) and a set of architectural patterns to make you write maintainable, solid end-to-end (GUI) tests. It automatically handles asynchronous operations without any work on your side.

An assertion library for JavaScript and Node.js with a friendly BDD syntax (awesome.must.be.true()). It ships with many expressive matchers and is test runner and framework agnostic. Follows RFC 2119 with its use of MUST. Good stuff and well tested.